Glass-ceramics with high elastic modulus and hardness

ABSTRACT

A composition includes 30 mol % to 60 mol % SiO2; 15 mol % to 40 mol % Al2O3; 5 mol % to 25 mol % Y2O3; 5 mol % to 15 mol % TiO2; and 0.1 mol % to 15 mol % RO, such that RO is a sum of MgO, CaO, SrO, and BaO.

This application is a continuation of U.S. application Ser. No. 17/331,050 filed on May 26, 2021, which claims the benefit of priority under 35 U.S.C. § 119 of U.S. Provisional Application Ser. No. 63/030,719, filed on May 27, 2020, and Korean Application Serial No. 10-2020-129314, filed on Oct. 7, 2020, the contents of both of which are relied upon and incorporated herein by reference in their entirety.

BACKGROUND 1. Field

The disclosure relates to novel glass and glass-ceramic compositions.

2. Technical Background

High strength glass and glass-ceramic materials are necessary for a broad range of applications including handheld devices, memory disks, and fibers. For glasses, sufficient mechanical attributes may be achieved with compositions containing high proportions of high field strength oxides (e.g., MgO, Y₂O₃, La₂O₃, etc.). Glass-ceramics pose a more complicated problem. Designing mechanically-advantaged glass-ceramics is more unpredictable, as precursor glass compositions do not necessarily indicate how the composite material (crystallites plus residual glass) will behave.

Thus, as described herein, novel glass and glass-ceramic compositions are disclosed having predictable, superior mechanical properties.

SUMMARY

In some embodiments, a composition comprises: 30 mol % to 60 mol % SiO₂; 15 mol % to 40 mol % Al₂O₃; 5 mol % to 25 mol % Y₂O₃; 5 mol % to 15 mol % TiO₂; and 0.1 mol % to 15 mol % RO, wherein RO is a sum of MgO, CaO, SrO, and BaO. In one aspect, which is combinable with any of the other aspects or embodiments, the composition comprises at least 4 mol % RO.

In one aspect, which is combinable with any of the other aspects or embodiments, RO comprises 0 mol % to 10 mol % MgO. In one aspect, which is combinable with any of the other aspects or embodiments, RO comprises 0 mol % to 10 mol % CaO. In one aspect, which is combinable with any of the other aspects or embodiments, RO comprises 0 mol % to 10 mol % SrO. In one aspect, which is combinable with any of the other aspects or embodiments, RO comprises 0 mol % to 10 mol % BaO.

In one aspect, which is combinable with any of the other aspects or embodiments, RO comprises a sum of at least two of MgO, CaO, SrO, and BaO. In one aspect, which is combinable with any of the other aspects or embodiments, RO comprises a sum of at least three of MgO, CaO, SrO, and BaO.

In one aspect, which is combinable with any of the other aspects or embodiments, the composition further comprises 0 mol % to 10 mol % B₂O₃.

In one aspect, which is combinable with any of the other aspects or embodiments, the composition further comprises 0.1 mol % to 6 mol % R₂O, wherein R₂O is a sum of Na₂O, K₂O, Li₂O, Rb₂O, and Cs₂O. In one aspect, which is combinable with any of the other aspects or embodiments, R₂O consists of Li₂O, Na₂O, or a combination thereof. In one aspect, which is combinable with any of the other aspects or embodiments, R₂O comprises 0 mol % to 5 mol % Li₂O. In one aspect, which is combinable with any of the other aspects or embodiments, R₂O comprises 0.1 mol % to 5 mol % Na₂O.

In one aspect, which is combinable with any of the other aspects or embodiments, the composition is a glass composition.

In one aspect, which is combinable with any of the other aspects or embodiments, the composition is a glass-ceramic composition. In one aspect, which is combinable with any of the other aspects or embodiments, the glass-ceramic composition comprises at least one of Y₂Ti₂O₇, Y₂Si₂O₇, or a combination thereof. In one aspect, which is combinable with any of the other aspects or embodiments, the glass-ceramic composition comprises at least one Mg-based compound. In one aspect, which is combinable with any of the other aspects or embodiments, the at least one Mg-based compound comprises Mg₂Al₄Si₅O₁₈, Mg₂SiO₄, Mg₄Al₈Si₂O₂₀, MgAl₂Si₃O₁₀, or a combination thereof. In one aspect, which is combinable with any of the other aspects or embodiments, the glass-ceramic composition comprises at least one Al-based compound. In one aspect, which is combinable with any of the other aspects or embodiments, the at least one Al-based compound comprises Y₃Al₅O₁₂, Al₂O₃, LiAlSi₂O₆, Al₆Si₂O₁₃, SrAl₂Si₂O₈, BaAl₂Si₂O₈.

In one aspect, which is combinable with any of the other aspects or embodiments, a ratio of RO to Al₂O₃ is in a range of 0.01 to 0.5.

In some embodiments, a glass composition described herein has a Young's modulus in a range of 117 GPa to 136 GPa. In some embodiments, a glass-ceramic composition described herein has a Young's modulus in a range of 150 GPa to 196 GPa.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure will become more fully understood from the following detailed description, taken in conjunction with the accompanying figures, in which:

FIG. 1 illustrates a plot comparing Young's modulus and density of glass-ceramics disclosed herein with various materials, according to some embodiments.

FIG. 2 illustrates a plot comparing Young's modulus of glass-ceramics disclosed herein with various known glass-ceramics, according to some embodiments.

FIGS. 3A-3C illustrate density (FIG. 3A), Young's modulus (FIG. 3B), and shear modulus (FIG. 3C) of glass-ceramics disclosed herein as a function of their respective precursor glass, according to some embodiments.

FIGS. 4A-4F illustrate microstructures of Sample A as a function of ceramming schedule, according to some embodiments.

FIGS. 5A-5D illustrate microstructures of Sample B as a function of ceramming schedule, according to some embodiments.

FIGS. 6A-6C illustrate microstructures of Sample E as a function of ceramming schedule, according to some embodiments.

DETAILED DESCRIPTION

In the following description, whenever a group is described as comprising at least one of a group of elements and combinations thereof, it is understood that the group may comprise, consist essentially of, or consist of any number of those elements recited, either individually or in combination with each other. Similarly, whenever a group is described as consisting of at least one of a group of elements or combinations thereof, it is understood that the group may consist of any number of those elements recited, either individually or in combination with each other. Unless otherwise specified, a range of values, when recited, includes both the upper and lower limits of the range as well as any ranges therebetween. It also is understood that the various features disclosed in the specification and the drawings can be used in any and all combinations.

Where a range of numerical values is recited herein, comprising upper and lower values, unless otherwise stated in specific circumstances, the range is intended to include the endpoints thereof, and all integers and fractions within the range. It is not intended that the scope of the claims be limited to the specific values recited when defining a range. Further, when an amount, concentration, or other value or parameter is given as a range, one or more preferred ranges or a list of upper preferable values and lower preferable values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether such pairs are separately disclosed. Finally, when the term “about” is used in describing a value or an end-point of a range, the disclosure should be understood to include the specific value or end-point referred to. When a numerical value or end-point of a range does not recite “about,” the numerical value or end-point of a range is intended to include two embodiments: one modified by “about,” and one not modified by “about.”

Herein, glass and glass-ceramic compositions are expressed in terms of mol % amounts of particular components included therein on an oxide bases unless otherwise indicated. Any component having more than one oxidation state may be present in a glass or glass-ceramic composition in any oxidation state. However, concentrations of such component are expressed in terms of the oxide in which such component is at its lowest oxidation state unless otherwise indicated.

Unless otherwise specified, all compositions are expressed in terms of mole percent (mol %). Young's modulus, shear modulus, and Poisson's ratio are all measured at the same time using Resonant Ultrasound Spectroscopy, which is conducted as set forth in ASTM E1875-00e1.

Glass and Glass-Ceramic Compositions

Novel compositions disclosed herein include mechanically-advantaged precursor glasses, as well as strong, high Young's modulus and high hardness glass-ceramics. The precursor glasses are unique because they comprise extremely high Al₂O₃ and Y₂O₃ contents, low SiO₂ contents, and RO modifiers. The glass-ceramics have novel phase assemblages as well as microstructures (e.g., homogenous and internally nucleated). Moreover, in addition to their inherent strength, the disclosed glass and glass-ceramic compositions may be chemically strengthened with high strain and anneal points, further increasing their damage resistance from surface flaws and potential for high temperature applications.

As referred to herein, “compositions” may refer to either “glass compositions” or “glass-ceramic compositions.” Substantial compositional equivalence is expected between the precursor glass and glass-ceramic after heat treatment (ceramming) of the precursor glass (explained below).

Silicon dioxide (SiO₂), which serves as the primary oxide component of the embodied compositions, may be included to provide high temperature stability and chemical durability. In some examples, compositions may comprise 30 mol % to 60 mol % SiO₂. In some examples, the composition may comprise 33 mol % to 37 mol % SiO₂. In some examples, the composition may comprise 30 mol % to 35 mol % SiO₂, or 35 mol % to 40 mol % SiO₂, or 40 mol % to 45 mol % SiO₂, or 45 mol % to 50 mol % SiO₂, or 50 mol % to 55 mol % SiO₂, or 55 mol % to 60 mol % SiO₂, or 30 mol % to 40 mol % SiO₂, or 35 mol % to 50 mol % SiO₂, or 40 mol % to 50 mol % SiO₂, or any value or range disclosed therein. In some examples, the composition is essentially free of SiO₂ or comprises 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50 mol % SiO₂, or any value or range having endpoints disclosed herein.

A network former is an oxide component of a glass that forms a backbone of the glass structure. Some examples include SiO₂, Al₂O₃, P₂O₅, and B₂O₃. Alumina (Al₂O₃) may influence the structure of the composition and, additionally, lower the liquidus temperature and coefficient of thermal expansion, or, enhance the strain point. In addition to its role as a network former, Al₂O₃ (and ZrO₂) help improve chemical durability in silicate-based compositions while having no toxicity concerns.

Moreover, alumina (Al₂O₃) advantageously contributes to increased mechanical strength of the composition. The compositions disclosed herein are unique due to their high Al₂O₃ contents. Along with yttria, alumina has amongst the most significant effect on increasing elastic modulus, E (GPa) of the glass or glass-ceramic compositions. At least due to the concentrations of alumina, glass compositions and glass-ceramic compositions are achieved having high Young's modulus values (117-136 GPa and 150-196 GPa, respectively).

In some examples, the composition may comprise 15 mol % to 40 mol % Al₂O₃. In some examples, the composition may comprise 24 mol % to 32 mol % Al₂O₃. In some examples, the composition may comprise 15 mol % to 20 mol % Al₂O₃, or 20 mol % to 25 mol % Al₂O₃, or 25 mol % to 30 mol % Al₂O₃, or 30 mol % to 35 mol % Al₂O₃, or 35 mol % to 40 mol % Al₂O₃, or 24 mol % to 30 mol % Al₂O₃, or 30 mol % to 32 mol % Al₂O₃, or 20 mol % to 35 mol % Al₂O₃, or 15 mol % to 25 mol % Al₂O₃, or 25 mol % to 40 mol % Al₂O₃, or any value or range disclosed therein. In some examples, the composition comprises 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40 mol % Al₂O₃, or any value or range having endpoints disclosed herein.

Zirconium dioxide (ZrO₂) behaves as a nucleating agent, which facilitates internal nucleation and is an important first step in crystallization. In some examples, the composition may comprise 0 mol % to 10 mol % ZrO₂. In some examples, the composition may comprise 0 mol % to 5 mol % ZrO₂. In some examples, the composition may comprise 0 mol % to 4 mol % ZrO₂, or 0.5 mol % to 3.5 mol % ZrO₂, or 1 mol % to 3 mol % ZrO₂, or any value or range disclosed therein. In some examples, the composition comprises 0, >0, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10 mol % ZrO₂, or any value or range having endpoints disclosed herein.

Alkali oxides (R₂O, which is the sum of Na₂O, K₂O, Li₂O, Rb₂O, and/or Cs₂O) serve as aids in achieving low melting temperature and low liquidus temperatures and/or help to improve bioactivity, if needed, and/or influence the coefficient of thermal expansion, especially at low temperatures. Li₂O-containing compositions can be ion-exchanged, resulting in a surface compressive stress and damage resistance. In some examples, the composition may comprise 0 mol % to 25 mol % R₂O. In some examples, the composition may comprise 0 mol % to 15 mol % R₂O. In some examples, the composition may comprise 0 mol % to 10 mol % Na₂O and Li₂O combined. In some examples, the composition may comprise 0 mol % to 9 mol %, or >0 mol % to 9 mol %, >0 mol % to 7 mol %, 1 mol % to 5 mol %, or 1 mol % to 4 mol % R₂O, or any value or range disclosed therein. In some examples, the composition may comprise >0 mol % to 5 mol % Na₂O, or >0 mol % to 3 mol % Na₂O, 3 mol % to 10 mol % Na₂O, or any value or range disclosed therein. In some examples, the composition may comprise 0 mol % to 5 mol % Li₂O, or 5 mol % to 10 mol % Li₂O, or any value or range disclosed therein. In some examples, the composition comprises 0, >0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25 mol % R₂O (e.g., Na₂O, K₂O, Li₂O, Rb₂O, Cs₂O, or combinations thereof), or any value or range having endpoints disclosed herein.

Yttrium oxide (Y₂O₃) advantageously contributes to increased mechanical strength of the composition. The compositions disclosed herein are unique due to their high Y₂O₃ contents. Along with alumina, yttria has amongst the most significant effect on increasing elastic modulus, E (GPa) of the glass or glass-ceramic compositions. At least due to the concentrations of yttria, glass compositions and glass-ceramic compositions are achieved having high Young's modulus values (117-136 GPa and 150-196 GPa, respectively).

For the glass compositions, these properties may be due to a high field strength of network modifiers in these glasses. The close packing structure occurs due to the high field strength and leads to high modulus, as well as high density and refractive index. For glass-ceramic compositions, various crystalline phases increase mechanical properties of the bulk materials relative to their precursor glasses (e.g., as explained in Example 4 below). The phases that contribute most to this increase in mechanical properties are Y₂Ti₂O₇, Y₂Si₂O₇, and Y₃Al₅O₁₂ (yttrium aluminum garnet, YAG). The increase in Young's modulus is achieved in both Li-only containing compositions, as well as glass-ceramic compositions comprising sodium (Na).

In some examples, the composition may comprise 5 mol % to 25 mol % Y₂O₃. In some examples, the composition may comprise 8 mol % to 14 mol % Y₂O₃. In some examples, the composition may comprise 10 mol % to 15 mol % Y₂O₃. In some examples, the composition may comprise 7 mol % to 23 mol % Y₂O₃ or 10 mol % to 20 mol % Y₂O₃, or any value or range disclosed therein. In some examples, the composition comprises 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25 mol % Y₂O₃, or any value or range having endpoints disclosed herein.

Diboron trioxide (B₂O₃) helps to lower liquidus temperature and increase the amount of residual glass in the glass-ceramic composition. At present, liquidus temperatures of the compositions disclosed herein are significantly lower than has been achieved for other glass-ceramics having comparably high Young's modulus, such as enstatite glass-ceramics. In some examples, the composition may comprise 0 mol % to 15 mol % B₂O₃. In some examples, the composition may comprise 0 mol % to 10 mol % B₂O₃. In some examples, the composition may comprise 0 mol % to 5 mol % B₂O₃, or 5 mol % to 10 mol % B₂O₃, or 10 mol % to 15 mol % B₂O₃, or any value or range disclosed therein. In some examples, the composition comprises 0, >0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 mol % B₂O₃, or any value or range having endpoints disclosed herein.

Titanium dioxide (TiO₂) behaves as a nucleating agent, which facilitates internal nucleation and is an important first step in crystallization. In some examples, the composition may comprise 0 mol % to 20 mol % TiO₂. In some examples, the composition may comprise 5 mol % to 15 mol % TiO₂. In some examples, the composition may comprise 5 mol % to 8 mol % TiO₂, or 8 mol % to 11 mol % TiO₂, or 11 mol % to 14 mol % TiO₂, or 14 mol % to 17 mol % TiO₂, or 17 mol % to 20 mol % TiO₂, or any value or range disclosed therein. In some examples, the composition comprises 0, >0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 mol % TiO₂, or any value or range having endpoints disclosed herein.

Other compositions may include phosphorus pentoxide (P₂O₅), network modifiers alkaline earth oxides (RO, which is the sum of MgO, CaO, SrO, and/or BaO) and zinc oxide (ZnO). Phosphorus pentoxide (P₂O₅) may also serve as a network former, as well as help to increase composition viscosity, which in turn expands the range of operating temperatures, and is therefore an advantage to the manufacture and formation of the glass and/or glass-ceramic composition. Alkaline earth oxides may improve desirable properties in the materials, including increasing Young's modulus and the coefficient of thermal expansion. In some examples, zinc oxide (ZnO) may behave similar to alkaline earth oxides (e.g., MgO).

In some examples, the composition may comprise 0 mol % to 40 mol % RO. In some examples, the composition may comprise 0 mol % to 25 mol % RO. In some examples, the composition may comprise 0 mol % to 15 mol % RO. In some examples, the composition may comprise >0 mol % to 15 mol %, or 1 mol % to 15 mol %, or 1 mol % to 12.5 mol %, or 4 mol % to 12.5 mol %, or 4 mol % to 10.5 mol % RO, or any value or range disclosed therein. In some examples, the composition may comprise 0 mol % to 10 mol % MgO, or 0 mol % to 5 mol % MgO, or 5 mol % to 10 mol % MgO, or any value or range disclosed therein. In some examples, the composition may comprise 0 mol % to 10 mol % CaO, or 0 mol % to 5 mol % CaO, 5 mol % to 10 mol % CaO, or any value or range disclosed therein. In some examples, the composition may comprise 0 mol % to 10 mol % SrO, or 0 mol % to 5 mol % SrO, 5 mol % to 10 mol % SrO, or any value or range disclosed therein. In some examples, the composition may comprise 0 mol % to 10 mol % BaO, or 0 mol % to 5 mol % BaO, 5 mol % to 10 mol % BaO, or any value or range disclosed therein. In some examples, the composition comprises 0, >0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40 mol % RO (e.g., MgO, CaO, SrO, BaO, or combinations thereof), or any value or range having endpoints disclosed herein.

Additional components can be incorporated into the composition to provide additional benefits or may be incorporated as contaminants typically found in commercially-prepared compositions. For example, additional components can be added as coloring or fining agents (e.g., to facilitate removal of gaseous inclusions from melted batch materials used to produce the composition) and/or for other purposes. In some examples, the composition may comprise one or more compounds useful as ultraviolet radiation absorbers. In some examples, the composition can comprise CeO, MnO, Nb₂O₅, MoO₃, Ta₂O₅, WO₃, SnO₂, Fe₂O₃, As₂O₃, Sb₂O₃, Cl, Br, or combinations thereof. The compositions, according to some examples, can also include various contaminants associated with batch materials and/or introduced into the composition by the melting, fining, and/or forming equipment used to produce the composition. For example, in some embodiments, the composition can comprise SnO₂ or Fe₂O₃, or combinations thereof.

In some examples, the composition comprises a combination of SiO₂, Al₂O₃, Na₂O, MgO, CaO, Y₂O₃, and TiO₂. In some examples, the composition comprises a combination of SiO₂, Al₂O₃, Li₂O, Na₂O, MgO, Y₂O₃, and TiO₂. In some examples, the composition comprises a combination of SiO₂, Al₂O₃, Na₂O, MgO, CaO, SrO, Y₂O₃, and TiO₂. In some examples, the composition comprises a combination of SiO₂, Al₂O₃, Li₂O, Na₂O, MgO, CaO, Y₂O₃, and TiO₂. In some examples, the composition comprises a combination of SiO₂, Al₂O₃, Na₂O, CaO, SrO, Y₂O₃, and TiO₂. In some examples, the composition comprises a combination of SiO₂, Al₂O₃, Li₂O, Na₂O, SrO, Y₂O₃, and TiO₂. In some examples, the composition comprises a combination of SiO₂, Al₂O₃, Na₂O, MgO, CaO, SrO, BaO, Y₂O₃, and TiO₂. In some examples, the composition comprises a combination of SiO₂, Al₂O₃, Na₂O, MgO, Y₂O₃, and TiO₂. In some examples, the composition comprises a combination of SiO₂, Al₂O₃, B₂O₃, Na₂O, MgO, Y₂O₃, and TiO₂.

In some examples, the composition comprises a combination of SiO₂, Al₂O₃, Na₂O, Y₂O₃, TiO₂, at least one of Li₂O or Na₂O, at least one of MgO, CaO, SrO, or BaO, and optionally B₂O₃. In some examples, the composition comprises a combination of SiO₂, Al₂O₃, Na₂O, Y₂O₃, TiO₂, at least one of Li₂O or Na₂O, at least two of MgO, CaO, SrO, or BaO, and optionally B₂O₃. In some examples, the composition comprises a combination of SiO₂, Al₂O₃, Na₂O, Y₂O₃, TiO₂, at least one of Li₂O or Na₂O, at least three of MgO, CaO, SrO, or BaO, and optionally B₂O₃. In some examples, the composition comprises a combination of SiO₂, Al₂O₃, Na₂O, Y₂O₃, TiO₂, at least one of Li₂O or Na₂O, all of MgO, CaO, SrO, or BaO, and optionally B₂O₃.

EXAMPLES

The embodiments described herein will be further clarified by the following examples.

Example 1—Precursor Glass Composition Formation

Glasses having the oxide contents listed in Table 1 can be made via traditional methods. In some examples, the precursor glasses can be formed by thoroughly mixing the requisite batch materials (for example, using a tubular mixer) in order to secure a homogeneous melt, and subsequently placing into silica and/or platinum crucibles. The crucibles can be placed into a furnace and the glass batch melted and maintained at temperatures ranging from 1100° C. to 1400° C. for times ranging from about 6 hours to 24 hours. The melts can thereafter be poured into steel molds to yield glass slabs. Subsequently, those slabs can be transferred immediately to an annealer operating at about 400° C. to 700° C., where the glass is held at temperature for about 0.5 hour to 3 hours and subsequently cooled overnight. In another non-limiting example, precursor glasses are prepared by dry blending the appropriate oxides and mineral sources for a time sufficient to thoroughly mix the ingredients. The glasses are melted in platinum crucibles at temperatures ranging from about 1100° C. to 1400° C. and held at temperature for about 6 hours to 16 hours. The resulting glass melts are then poured onto a steel table to cool. The precursor glasses are then annealed at appropriate temperatures.

The embodied glass compositions can be ground into fine particles in the range of 1-10 microns (m) by air jet milling or short fibers. The particle size can be varied in the range of 1-100 μm using attrition milling or ball milling of glass frits. Furthermore, these glasses can be processed into short fibers, beads, sheets or three-dimensional scaffolds using different methods. Short fibers are made by melt spinning or electric spinning; beads can be produced by flowing glass particles through a hot vertical furnace or a flame torch; sheets can be manufactured using thin rolling, float or fusion-draw processes; and scaffolds can be produced using rapid prototyping, polymer foam replication and particle sintering.

Continuous fibers can be easily drawn from the claimed composition using processes known in the art. For example, fibers can be formed using a directly heated (electricity passing directly through) platinum bushing. Glass cullet is loaded into the bushing, heated up until the glass can melt. Temperatures are set to achieve a desired glass viscosity (usually <1000 poise) allowing a drip to form on the orifice in the bushing (Bushing size is selected to create a restriction that influences possible fiber diameter ranges). The drip is pulled by hand to begin forming a fiber. Once a fiber is established it is connected to a rotating pulling/collection drum to continue the pulling process at a consistent speed. Using the drum speed (or revolutions per minute RPM) and glass viscosity the fiber diameter can be manipulated—in general the faster the pull speed, the smaller the fiber diameter. Glass fibers with diameters in the range of 1-100 μm can be drawn continuously from a glass melt. Fibers can also be created using an updraw process. In this process, fibers are pulled from a glass melt surface sitting in a box furnace. By controlling the viscosity of the glass, a quartz rod is used to pull glass from the melt surface to form a fiber. The fiber can be continuously pulled upward to increase the fiber length. The velocity that the rod is pulled up determines the fiber thickness along with the viscosity of the glass.

Example 2—Precursor Glass Compositions

Non-limiting examples of amounts of oxides for forming the precursor glasses are listed in Table 1.

TABLE 1 Mol % A B C D E F G H I SiO₂ 34.2 34.9 34.4 34.4 34.2 34.6 34.1 36.3 33.3 Al₂O₃ 31.1 30.6 30.5 30.7 30.8 30.7 30.7 27.2 24.7 B₂O₃ — — — — — — — — 8.8 Li₂O — 4.5 — 4.8 — 4.7 — — — Na₂O 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.1 MgO 9.4 4.6 0.1 0.1 — — 0.1 9.9 9.1 CaO 0.1 — 9.9 5.0 0.1 — 0.1 — — SrO — — 0.1 — 9.9 5.0 0.3 — — BaO — — — — — — 9.3 — — Y₂O₃ 11.9 12.0 11.8 11.8 11.7 11.7 12.0 12.4 11.3 TiO₂ 13.1 13.0 13.0 13.0 13.1 13.0 13.2 13.9 12.6 Sum 100 100 100 100 100 100 100 100 100 R₂O/Al₂O₃ 0.01 0.15 0.01 0.16 0.01 0.16 0.01 0.01 0.01 RO/Al₂O₃ 0.31 0.15 0.33 0.16 0.32 0.16 0.32 0.37 0.37

The ratios of R₂O to Al₂O₃ and RO to Al₂O₃ are important for determining the charge-balance of the precursor glass, assuming all R⁺ first goes to charge balance Al³⁺. In other words, the ratios of R₂O to Al₂O₃ and RO to Al₂O₃ are important for glass composition design because they represent the charge balance of the composition, which has a significant influence on composition structure and thus, its properties. Charge balance is also important in determining the ease in forming a glass. The ratios of R₂O to Al₂O₃ and RO to Al₂O₃ are similar in terms of charge compensation of the Al³⁺ (e.g., when Al³⁺ replaces Si⁴⁺) in the glass network. For R₂O (alkali ‘R’), one alkali R (e.g., Na) is needed to charge balance since alkalis have a plus one charge. For RO (alkaline earth ‘R’), half an alkaline earth (e.g., Ca) is needed to charge balance since alkaline earths have a plus two charge.

The glass compositions disclosed herein can be in any form, for example, particles, powder, microspheres, fibers, sheets, beads, scaffolds, woven fibers.

Example 3—Precursor Glass Composition Properties

Young's modulus, shear modulus, and Poisson's ratio are all measured at the same time using Resonant Ultrasound Spectroscopy, which is conducted as set forth in ASTM E1875-00e1.

TABLE 2 A B C D E F G H I Density (g/cm³) 3.453 3.390 3.419 3.373 3.527 3.429 3.607 — — Poisson's Ratio 0.283 0.278 0.280 0.277 0.279 0.277 0.278 — — Young's Modulus, E (GPa) 136 133 128 129 123 126 117 — — Shear Modulus, G (GPa) 52.9 52.1 49.9 50.5 47.8 49.4 45.9 — —

The data in Table 2 illustrates the very high Young's modulus values of the precursor glasses. In comparison, typical glass compositions have Young's modulus values of only about 75 GPa.

Example 4—Glass-Ceramic Composition Properties

After forming and testing the precursor glasses as described in Examples 1-3, the precursor glasses were subjected to a heat treatment (i.e., ceramming) as follows: (a) a first temperature ramp from room temperature (RT) to a nucleation step temperature at 5° C./min; (b) a first isothermal hold at the nucleation step temperature for a first predetermined time; (c) a second temperature ramp from the nucleation step temperature to a crystallization step temperature at 5° C./min; (d) a second isothermal hold at the crystallization step temperature for a second predetermined time; and (e) a final cooling from the crystallization step temperature to room temperature at the natural rate of cooling within the furnace.

Tables 3-5 shows properties of the glass-ceramics formed as a result of the ceramming treatment. Characterization of the glass-ceramic Young's modulus, shear modulus, and Poisson's Ratio were conducted as described above in Example 3.

TABLE 3 Ceramming Schedule Nucleation Temp, 1st Isothermal Hold Crystallization Temp, 850° C., 2 hrs 2 d Isothermal Hold 1050° C., 4 hrs A B C D Density, ρ (g/cm³) 3.682 3.644 3.731 3.632 Δρ (%) from Precursor Glass 6.6  7.5 9.1 7.7 Poisson's Ratio 0.256 0.289 0.267 Young's Modulus, E (GPa) 178 150 167 ΔE (%) from Precursor Glass 33.4 17.1 29.4 Shear Modulus, G (GPa) 70.6 58.0 65.8 ΔG (%) from Precursor Glass 35.6 16.2 30.3 XRD - Phase 1 Y₂Si₂O₇ Y₂Ti₂O₇ Y₂Si₂O₇ Y₂Ti₂O₇ XRD - Phase 2 Y₂Ti₂O₇ MgAl₂Si₃O₁₀ Y₂Si₂O₇ LiAlSi₂O₆ (2nd polymorph) XRD - Phase 3 Mg₂SiO₄ Y₂Si₂O₇ XRD - Phase 4 Al₂O₃ Ceramming Schedule Nucleation Temp, 1st Isothermal Hold Crystallization Temp, 850° C., 2 hrs 2 d Isothermal Hold 1050° C., 4 hrs E F G Density, ρ (g/cm³) 3.833 3.650 3.809 Δρ (%) from Precursor Glass 8.7  6.4 5.6 Poisson's Ratio 0.276 0.276 Young's Modulus, E (GPa) 160 158 ΔE (%) from Precursor Glass 26.9 34.9 Shear Modulus, G (GPa) 62.7 62.0 ΔG (%) from Precursor Glass 27.0 35.0 XRD - Phase 1 Y₂Ti₂O₇ Y₂Ti₂O₇ Y₂Ti₂O₇ XRD - Phase 2 SrAl₂Si₂O₈ LiAlSi₂O₆ BaAl₂Si₂O₈ XRD - Phase 3 Y₂Si₂O₇ Y₂Si₂O₇ XRD - Phase 4

TABLE 4 Ceramming Schedule Nucleation Temp, 1st Isothermal Hold Crystallization Temp, 850° C., 2 hrs 2 d Isothermal Hold 1150° C., 4 hrs A B D Density, ρ (g/cm³) 3.651 3.584 3.626 Δρ (%) from Precursor Glass 5.7 5.7 7.5 Poisson's Ratio 0.280 0.270 0.272 Young's Modulus, E (GPa) 196 186 162 ΔE (%) from Precursor Glass 44.3 39.5 25.3 Shear Modulus, G (GPa) 76.5 73.1 63.5 ΔG (%) from Precursor Glass 44.6 40.4 25.8 XRD - Phase 1 Y₂Ti₂O₇ Y₂Ti₂O₇ Y₂Ti₂O₇ XRD - Phase 2 Y₂Si₂O₇ Y₂Si₂O₇ LiAlSi₂O₆ XRD - Phase 3 Mullite: Al₆Si₂O₁₃ Mullite: Al₆Si₂O₁₃ XRD - Phase 4 Cordierite: LiAlSi₂O₆ Mg₂Al₄Si₅O₁₈ XRD - Phase 5 Spinel: Mg₂SiO₄ Spinel: Mg₂SiO₄ Ceramming Schedule Nucleation Temp, 1st Isothermal Hold Crystallization Temp, 850° C., 2 hrs 2 d Isothermal Hold 1150° C., 4 hrs E F G Density, ρ (g/cm³) 3.814 3.679 3.802 Δρ (%) from Precursor Glass 8.1  7.3 5.4  Poisson's Ratio 0.273 Young's Modulus, E (GPa) 158 ΔE (%) from Precursor Glass 25.3 Shear Modulus, G (GPa) 62.1 ΔG (%) from Precursor Glass 25.7 XRD - Phase 1 Y₂Ti₂O₇ Y₂Ti₂O₇ Y₂Ti₂O₇ XRD - Phase 2 SrAl₂Si₂O₈ LiAlSi₂O₆ BaAl₂Si₂O₈ XRD - Phase 3 Y₂Si₂O₇ Y₂Si₂O₇ XRD - Phase 4 XRD - Phase 5

TABLE 5 Ceramming Schedule Nucleation Temp, 1st Isothermal Hold Crystallization Temp, 850° C., 2 hrs 2 d Isothermal Hold 1250° C., 4 hrs A G Density, ρ (g/cm³) 3.657 Δρ (%) from 5.9  Precursor Glass XRD - Phase 1 Y₂Ti₂O₇ BaAl₂Si₂O₈ XRD - Phase 2 Y₂Si₂O₇ Y₂Ti₂O₇ XRD - Phase 3 Mullite - Al₆Si₂O₁₃ Y₂Si₂O₇ XRD - Phase 4 Spinel - Mg₂SiO₄ XRD - Phase 5 Sapphrine - (Mg₄Al₈Si₂O₂₀) XRD - Phase 6 Cordierite - Mg₂Al₄Si₅O₁₈

Example 5—Property Comparisons

FIGS. 1 and 2 illustrate plots comparing Young's modulus of glass-ceramics disclosed herein with various materials, including known glass-ceramics. Specific to FIG. 1 , the glass-ceramics of the present application have Young's modulus and density characteristics equivalent to the technical ceramics and metal region of the property space in the plot, indicating high-strength glass-ceramic materials with superior mechanical attributes needed for handheld device, memory disk, and fiber applications, among others.

FIG. 2 shows a comparison of the Young's modulus of glass-ceramic Samples A-D, F and G after subjecting their respective precursor glasses to either ceram schedule 1 (nucleation temperature hold at 850° C. for 2 hrs; crystallization temperature hold at 1050° C. for 4 hrs) or ceram schedule 2 (nucleation temperature hold at 850° C. for 2 hrs; crystallization temperature hold at 1150° C. for 4 hrs). Each of the tested samples have a Young's modulus of at least 150 GPa, which is higher than any of the known glass-ceramics (squares). Young's modulus of Samples A-D, F and G are summarized in Table 6 below, and the same for the known glass-ceramics in Table 7.

TABLE 6 Samples A-2 B-1 B-2 C-1 D-1 D-2 F-1 F-2 G-1 Young's Modulus, E (GPa) 196 178 186 150 167 162 160 158 158 ΔE (%) from Precursor Glass 44.3 33.4 39.5 17.1 29.4 25.3 26.9 25.3 34.9

TABLE 7 Glass-Ceramic Young's Modulus, E (GPa) Nepheline (K⁺--> Na⁺ IX) 73 Canasite 82 F-K-richterite, glazed 87 Empress ® 2 (Dental) 90 Cerabone ® Apatite-Wollastonite 118 Pyroceram ® 121 Cordierite-Enstatite 130 Enstatite 140

FIGS. 3A-3C illustrate density (FIG. 3A), Young's modulus (FIG. 3B), and shear modulus (FIG. 3C) of glass-ceramics disclosed herein as a function of their respective precursor glass. Specifically, FIGS. 3A-3C show the unexpected percent increase of each of the density, Young's modulus, and shear modulus, respectively, after their respective precursor glasses have undergone ceramming. Data of FIG. 3B is tabulated above in Table 6. The average increase in Young's modulus of the glass-ceramics whose precursor glass have undergone ceram schedule 1 (i.e., B-1, C-1, D-1, F-1, and G-1) is about 28.3%. The average increase in Young's modulus of the glass-ceramics whose precursor glass have undergone ceram schedule 2 (i.e., A-2, B-2, D-2, and F-2) is about 33.6%. Overall, the average increase in Young's modulus of the glass-ceramics whose precursor glass have undergone any ceram schedule disclosed herein is 30.7%, which is much higher than percent increases seen in conventional glass-ceramics systems (e.g., about 3 to 8% for spinel glass-ceramics).

Data of FIGS. 3A and 3C are tabulated below in Table 8.

TABLE 8 Samples A-1 B-1 C-1 D-1 E-1 F-1 G-1 Density, ρ (g/cm³) 3.682 3.644 3.731 3.632 3.833 3.650 3.809 Δρ (%) from Precursor Glass 6.6 7.5 9.1 7.7 8.7 6.4 5.6 Shear Modulus, G (GPa) — 70.6 58.0 65.8 — 62.7 62.0 ΔG (%) from Precursor Glass — 35.6 16.2 30.3 — 27.0 35.0 Samples A-2 B-2 D-2 E-2 F-2 G-2 Density, ρ (g/cm³) 3.651 3.584 3.626 3.814 3.679 3.802 Δρ (%) from Precursor Glass 5.7 5.7 7.5 8.1 7.3 5.4 Shear Modulus, G (GPa) 76.5 73.1 63.5 — 62.1 — ΔG (%) from Precursor Glass 44.6 40.4 25.8 — 25.7 —

The average increase in density of the glass-ceramics whose precursor glass have undergone ceram schedule 1 (i.e., A-1 to G-1) is about 7.4%. The average increase in density of the glass-ceramics whose precursor glass have undergone ceram schedule 2 (i.e., A-2, B-2, and D-2 to G-2) is about 6.6%. Overall, the average increase in density of the glass-ceramics whose precursor glass have undergone any ceram schedule disclosed herein is 7.0%, which is much higher than percent increases seen in conventional glass-ceramics systems (e.g., about 1 to 3%).

The average increase in Shear modulus of the glass-ceramics whose precursor glass have undergone ceram schedule 1 (i.e., B-1 to D-1, F-1, and G-1) is about 28.8%. The average increase in Shear modulus of the glass-ceramics whose precursor glass have undergone ceram schedule 2 (i.e., A-2, B-2, D-2, and F-2) is about 34.1%. Overall, the average increase in Shear modulus of the glass-ceramics whose precursor glass have undergone any ceram schedule disclosed herein is 31.2%, which is much higher than percent increases seen in conventional glass-ceramics systems.

Example 6—Microstructure Imaging

FIGS. 4A-4F illustrate microstructures of Sample A as a function of ceramming schedule, summarized in Table 9 below.

TABLE 9 FIGS. 4A 4B 4C 4D 4E 4F Ceramming (1) 850° C. for 2 hrs (1) 850° C. for 2 hrs (1) 850° C. for 2 hrs Schedule (2) 1050° C. for 4 hrs (2) 1150° C. for 4 hrs (2) 1250° C. for 4 hrs Description Internal nucleation Internal nucleation Internal nucleation & high crystallinity & high crystallinity & high crystallinity Grains significantly larger than in FIGS. 4A-4D

FIGS. 5A-5D illustrate microstructures of Sample B as a function of ceramming schedule, summarized in Table 10 below.

TABLE 10 FIGS. 5A 5B 5C 5D z z z z z Ceramming (1) 850° C. for 2 hrs (1) 850° C. for 2 hrs Schedule (2) 1050° C. for 4 hrs (2) 1150° C. for 4 hrs Description Internalnucleation & high Internalnucleation crystallinity with very & high crystallinity small grain size

FIGS. 6A-6C illustrate microstructures of Sample E as a function of ceramming schedule, summarized in Table 11 below.

TABLE 11 FIGS. 6A 6B 6C z z z z Ceramming (1) 850° C. for 2 hrs Schedule (2) 1050° C. for 4 hrs Description Internalnucleation & high crystallinity with large laths. Interlinked lath-like microstructures cause increased mechanical properties (e.g., fracture toughness, strength, etc.)

FIGS. 4A-4F illustrate microstructures of Sample A, comprising a majority RO (i.e., alkaline earth metal oxide) modifier (9.4 mol % MgO and 0.1 mol % CaO) and trace R₂O (alkali oxide) modifier (0.2 mol % Na₂O). FIGS. 5A-5D illustrate microstructures of Sample B, comprising a roughly 50% RO modifier (4.6 mol % MgO) and 50% R₂O modifier (4.5 mol % Li₂O and 0.2 mol % Na₂O). FIGS. 6A-6C illustrate microstructures of Sample E, comprising a majority RO modifier (9.9 mol % SrO and 0.1 mol % CaO) and trace R₂O modifier (0.2 mol % Na₂O). The presence of at least one RO modifier, as compared with glass-ceramic compositions with 100% R₂O modifiers results in bulk compositions with unique microstructures and even higher Young's modulus. For example, for each composition with a different RO modifier, a novel and unique phase assemblage is observed, with all glass-ceramic compositions having between three and six crystalline phases, very low amounts of residual glass, and no microcracking due to thermal expansion mismatches. All glass-ceramic materials disclosed herein are internally nucleated (i.e., nucleation that is formed from within the bulk of a material as opposed to from the material's surface) and homogeneous throughout the bulk, with grain size highly dependent on individual composition and ceram schedule.

Thus, as presented herein, novel glass and glass-ceramic compositions are disclosed having predictable, superior mechanical properties. The mechanical and elastic behavior of the glass compositions disclosed herein are superior to many commercially-available glass compositions. For example, compositions typically used in handheld device, memory disk, and fiber applications have a Young's modulus of about 65 GPa to 75 GPa, whereas Young's modulus of the glass compositions disclosed herein range much higher, at between 117 GPa to 136 GPa. These values are sufficiently high that the precursor glasses of the disclosed glass-ceramics are competitive with many transparent glass-ceramics, a significant feat for fully amorphous materials. Additionally, the precursor glass compositions of the present applications may be chemically strengthened while also having high fracture toughness and hardness.

After heat-treatment, the glass compositions become opaque, forming white glass-ceramics even more mechanically advantaged than the precursor glasses (i.e., having higher modulus values). The range of glass-ceramic Young's modulus values is 150 GPa to 196 GPa, depending on composition and ceramming schedule. Fracture toughness typically scales with Young's modulus, suggesting these materials also have high fracture toughness, and thus, an improved strength for a given flaw size population as compared to materials with lower fracture toughness values (e.g., more typical glasses). Moreover, the glass-ceramics formed from the precursor glass are fully-dense materials having high resistance to thermal deformation. The glass-ceramics disclosed herein are high in Y₂O₃ content, low in Al₂O₃ and SiO₂ content, and include alkaline earth (RO) modifiers. Because glass-ceramics of the present application may be formed without alkali (R₂O) modifiers, these compositions may be used for applications where alkali components are unnecessary and/or detrimental, such as many display or substrate applications.

As used herein, the term “and/or,” when used in a list of two or more items, means that any one of the listed items can be employed by itself, or any combination of two or more of the listed items can be employed. For example, if a composition is described as containing components A, B, and/or C, the composition can contain A alone; B alone; C alone; A and B in combination; A and C in combination; B and C in combination; or A, B, and C in combination.

References herein to the positions of elements (e.g., “top,” “bottom,” “above,” “below,” “first,” “second,” etc.) are merely used to describe the orientation of various elements in the FIGURES. It should be noted that the orientation of various elements may differ according to other exemplary embodiments, and that such variations are intended to be encompassed by the present disclosure. Moreover, these relational terms are used solely to distinguish one entity or action from another entity or action, without necessarily requiring or implying any actual such relationship or order between such entities or actions.

Modifications of the disclosure will occur to those skilled in the art and to those who make or use the disclosure. Therefore, it is understood that the embodiments shown in the drawings and described above are merely for illustrative purposes and not intended to limit the scope of the disclosure, which is defined by the following claims, as interpreted according to the principles of patent law, including the doctrine of equivalents.

It will be understood by one having ordinary skill in the art that construction of the described disclosure, and other components, is not limited to any specific material. Other exemplary embodiments of the disclosure disclosed herein may be formed from a wide variety of materials, unless described otherwise herein.

As utilized herein, the terms “approximately,” “about,” “substantially”, and similar terms are intended to have a broad meaning in harmony with the common and accepted usage by those of ordinary skill in the art to which the subject matter of this disclosure pertains. It should be understood by those of skill in the art who review this disclosure that these terms are intended to allow a description of certain features described and claimed without restricting the scope of these features to the precise numerical ranges provided. Accordingly, these terms should be interpreted as indicating that insubstantial or inconsequential modifications or alterations of the subject matter described and claimed are considered to be within the scope of the invention as recited in the appended claims. In other words, the terms “about,” “approximately,” and the like, mean that amounts, sizes, formulations, parameters, and other quantities and characteristics are not and need not be exact, but may be approximate and/or larger or smaller, as desired, reflecting tolerances, conversion factors, rounding off, measurement error and the like, and other factors known to those of skill in the art.

Thus, a glass that is “free” or “essentially free” of a component is one in which that component is not actively added or batched into the glass, but may be present in very small amounts as a contaminant (e.g., 500, 400, 300, 200, or 100 parts per million (ppm) or less or).

As utilized herein, “optional,” “optionally,” or the like are intended to mean that the subsequently described event or circumstance can or cannot occur, and that the description includes instances where the event or circumstance occurs and instances where it does not occur. As used herein, the indefinite articles “a,” “an,” and the corresponding definite article “the” mean “at least one” or “one or more,” unless otherwise specified.

With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for the sake of clarity.

Unless otherwise specified, all compositions are expressed in terms of as-batched mole percent (mol %). As will be understood by those having ordinary skill in the art, various melt constituents (e.g., silicon, alkali- or alkaline-based, boron, etc.) may be subject to different levels of volatilization (e.g., as a function of vapor pressure, melt time and/or melt temperature) during melting of the constituents. As such, the as-batched mole percent values used in relation to such constituents are intended to encompass values within ±0.5 mol % of these constituents in final, as-melted articles. With the forgoing in mind, substantial compositional equivalence between final articles (glass-ceramic compositions) and as-batched compositions (precursor glasses) is expected. For example, substantial compositional equivalence is expected between the precursor glass and glass-ceramic after the step of heat treatment (ceramming).

It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit or scope of the claimed subject matter. Accordingly, the claimed subject matter is not to be restricted except in light of the attached claims and their equivalents. 

What is claimed is:
 1. Glass-ceramic, comprising: glass; and crystals within the glass, the crystals comprising a phase of Y₂Si₂O₇ and/or Y₂Ti₂O₇.
 2. The glass-ceramic of claim 1, wherein the glass and the crystals together form a bulk, and wherein the crystals are homogeneous throughout the bulk.
 3. The glass-ceramic of claim 2, wherein the crystals have at least two phases, and wherein the first phase is Y₂Ti₂O₇.
 4. The glass-ceramic of claim 3, wherein the second phase comprises Y₂Si₂O₇ or crystals comprising aluminum, silicon, and oxygen.
 5. A method of making the glass-ceramic of claim 2, comprising: first holding a precursor at a nucleation temperature; and then holding the precursor at a crystallization temperature.
 6. The method of claim 5, wherein the precursor comprises 5 mol % to 25 mol % Y₂O₃.
 7. The method of claim 6, wherein the precursor comprises 5 mol % to 15 mol % TiO₂.
 8. The method of claim 7, wherein the precursor comprises 0.1 mol % to 6 mol % R₂O, where R₂O is a sum of Na₂O, K₂O, Li₂O, Rb₂O, and Cs₂O.
 9. The method of claim 8, wherein the precursor comprises 0.1 mol % to 15 mol % RO, where RO is a sum of MgO, CaO, SrO, and BaO.
 10. The method of claim 9, wherein the precursor comprises 15 mol % to 40 mol % Al₂O₃.
 11. The method of claim 10, wherein the precursor comprises 30 mol % to 60 mol % SiO₂.
 12. A method of making the glass-ceramic of claim 1, comprising: internally nucleating the crystals in a precursor; and growing the crystals in the precursor.
 13. A method of making the glass-ceramic of claim 1, comprising: ceramming a precursor to grow crystals within the precursor, wherein the glass and the crystals together form a bulk, and wherein the crystals are homogeneous throughout the bulk.
 14. The method of claim 13, wherein the crystals have at least two phases, and wherein the first phase is Y₂Ti₂O₇.
 15. The method of claim 13, wherein the second phase comprises Y₂Si₂O₇ or crystals comprising aluminum, silicon, and oxygen.
 16. The method of claim 13, wherein the precursor comprises 5 mol % to 25 mol % Y₂O₃.
 17. The method of claim 13, wherein the precursor comprises 5 mol % to 15 mol % TiO₂.
 18. The method of claim 13, wherein the precursor comprises 0.1 mol % to 6 mol % R₂O, where R₂O is a sum of Na₂O, K₂O, Li₂O, Rb₂O, and Cs₂O.
 19. The method of claim 13, wherein the precursor comprises 0.1 mol % to 15 mol % RO, where RO is a sum of MgO, CaO, SrO, and BaO.
 20. The method of claim 13, wherein the precursor comprises 15 mol % to 40 mol % Al₂O₃ and 30 mol % to 60 mol % SiO₂. 